Tuesday, December 7, 2010

The sci-fi inventions that maths predicts are possible

The eminent physicist Prof Amos Ori, of the Technion-Israel Institute of Technology, has set out a theoretical model of a time machine which would allow people to travel back in time to explore the past. The way the machine would work rests on Einstein’s theory of general relativity, a theory of gravity that shows how time can be warped by the gravitational pull of objects. Bend time enough and you can create a loop and the possibility of temporal travel. Prof Ori’s theory, set out in the prestigious science journal Physical Review, rests on a set of mathematical equations describing hypothetical conditions that, if established, could lead to the formation of a time machine, technically known as “closed time-like curves.” In the blends of space and time, or spacetime, in his equations, time would be able to curve back on itself, so that a person travelling around the loop might be able to go further back in time with each lap.

A rippling magic carpet that can fly through the air is a theoretical possibility, according to a Professor Lakshminarayanan Mahadevan of Harvard University. Fictional flying carpets are ubiquitous and have appeared in literature since ancient times. Now they have caught the attention of a leading mathematician. Although he has only succeeded in showing that flying is practical for a bank note sized carpet, Prof Mahadevan, and his co-workers believe that one capable of ferrying a person is far from being a pantomime fantasy. His claims were published in the journal Physical Review Letters. The key to levitating a carpet is to create uplift by making ripples that push against air close to a horizontal surface, such as a floor. The undulating movements create a high pressure in the gap between the carpet and the floor, "roughly balancing its weight." The magical part comes from the discovery that, as well as lifting it, the ripples can drive the carpet forward - a handy trick for a panto - because they make the carpet tilt slightly, moving towards the raised edge.

Warp speed

Two physicists have devised a scheme to travel faster than the speed of light. The advance could mean that Star Trek fantasies of interstellar civilisations and voyages powered by warp drive are now no longer the exclusive domain of science fiction writers. Dr Gerald Cleaver, associate professor of physics at Baylor, and Richard Obousy have come up with a new twist on an existing idea to produce a warp drive that they believe can travel faster than the speed of light, without breaking the laws of physics. In their scheme, in the Journal of the British Interplanetary Society, a starship could "warp" space so that it shrinks ahead of the vessel and expands behind it. By pushing the departure point many light years backwards while simultaneously bringing distant stars and other destinations closer, the warp drive effectively transports the starship from place to place at faster-than-light speeds. All this extraordinary feat requires, says the new study, is for scientists to harness a mysterious and poorly understood cosmic antigravity force, called dark energy. Dark energy is thought responsible for speeding up the expansion rate of our universe as time moves on, just like it did after the Big Bang, when the universe expanded much faster than the speed of light for a very brief time. This may come as a surprise since, according to relativity theory, matter cannot move through space faster than the speed of light, which is almost 300,000,000 metres per second. But that theory applies only to unwarped 'flat' space.


Professor Ulf Leonhardt and Dr Thomas Philbin, from the University of St Andrews in Scotland, have worked out a way of reversing a pheneomenon known as the Casimir force, a force of nature which normally causes objects to stick together.Their discovery could ultimately lead to frictionless micro-machines with moving parts that levitate. But they say that, in principle at least, the same effect could be used to levitate bigger objects too, even a person. The Casimir force is a consequence of quantum mechanics, the theory that describes the world of atoms and subatomic particles that is not only the most successful theory of physics but also the most baffling. The force is due to neither electrical charge or gravity, for example, but the fluctuations in all-pervasive energy fields in the intervening empty space between the objects and is one reason atoms stick together, also explaining a “dry glue” effect that enables a gecko to walk across a ceiling. Now, using a special lens of a kind that has already been built, Prof Ulf Leonhardt and Dr Thomas Philbin report in the New Journal of Physics they can engineer the Casimir force to repel, rather than attact.

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